Supplementary Material for: Mazabraud syndrome associated with McCune-Albright syndrome: a case report and literature review

The Mazabraud syndrome is a rare form of bone fibrous dysplasia associated with intramuscular myxomas. The McCune-Albright syndrome is characterized by the association of dysplasia fibrous bone to one or more extra-osseous manifestations, including café-au-lait skin spots and endocrine disturbances. Here, we report on a new case of a 52-year-old man with sacroiliac polyostic bone fibrous dysplasia associated with intramuscular myxomas of the left buttock and thigh and café-au-lait skin spot. Biopsy analysis of one muscular lesions on the left thigh analysis revealed a spindle cell tumor with myxoid stroma with GNAS gene mutation, confirming the diagnosis of intramuscular myxoma. Given the absence of radiological sign of malignancy at the bone level and a few pains relieved by simple analgesics, no specific treatment was applied. In March 2022, after 18 months of follow-up, the MRI and the PET-CT scan showed a stable disease. To our knowledge this case is the fourth one reporting association of Mazabraud syndrome and McCune-Albright syndrome in a man. The association of intramuscular tumors and bone tumors in the same anatomical region and without any continuity, especially in lower limbs, must evoke the diagnosis of Mazabraud syndrome.